Friction drive belts, such as V-belts and V-ribbed belts whose belt body includes a pulley contacting portion made of a rubber composition, are widely used for driving vehicle accessories, etc. Mixing carbon black in the rubber composition which forms the pulley contacting portion is a well-known technique.
Patent Document 1 discloses a transmission belt whose transmission face is made of a rubber composition in which 50 to 100 parts by mass of carbon black relative to 100 parts by mass of a rubber component is mixed. Ethylene-α-olefin copolymer rubber is used as the rubber component, and the carbon black contains high structure carbon whose nitrogen absorption specific surface area is 45 to 80 m2/g and DBP oil absorption specific area is 120 cm3/100 g or more, in an amount of 20 parts by mass or more relative to 100 parts by mass of the rubber component.
Here, it is known that in a belt transmission system for driving vehicle accessories, a phenomenon called “stick-slip” occurs when the belt is wet, and slip sound is generated by the slip between the belt and pulley. This slip sound may become a source of noise. Thus, various measures are taken.
For example, Patent Document 2 discloses a transmission belt whose transmission surface is made of a rubber composition containing an inorganic filler. The inorganic filler is a hydrophilic inorganic filler of a hydrophilic inorganic substance which has hydroxyl groups or water molecules, or a hydrophilic inorganic substance precursor which reacts with water to form a hydrophilic inorganic substance. The rubber composition contains 5 parts by mass or more of the hydrophilic inorganic filler relative to 100 parts may mass of rubber.
Patent Document 3 discloses a transmission belt in which at least part of a rubber portion of the belt contains short fibers. Ethylene-propylene-diene rubber whose iodine number is 3 or more and less than 40 is used as a rubber component. Nylon short fibers are singly used as the short fibers, and the mixing amount of the short fibers is 20 to 50 parts by mass relative to 100 parts by mass of the rubber.
Patent Document 4 discloses a V-ribbed belt of which a compression rubber layer as a pulley contact portion is made of a rubber composition in which 3 to 25 parts by mass of nylon resin powders relative to 100 parts by mass of a rubber component are mixed.
Patent Document 5 discloses a V-ribbed belt of which a compression rubber layer as a pulley contact portion is made of a rubber composition in which 1 to 15 parts by mass of porous acrylic short fibers relative to 100 parts by mass of a rubber component are mixed.
Patent Document 6 discloses a V-ribbed belt whose compression rubber layer is made of a rubber composition in which ethylene-α-olefin elastomer is used as a rubber component; short fibers are added to the rubber component in a total amount of 10 to 40 parts by mass relative to 100 parts by mass of the rubber component; the short fibers include aramid fibers in 35-100 mass percent of the total amount of the short fibers added; and 25-55 parts by mass of carbon black is added.
Patent Document 7 discloses a V-ribbed belt whose compression rubber layer as a pulley contact portion is made of a rubber composition in which 1 to 15 parts by mass of very short fibers which have a fiber length of 0.1 to 1.0 mm and water content of 6 to 20%, relative to 100 parts by mass of a rubber component, are mixed.
Patent Document 8 discloses that at least ribs of a V-ribbed belt includes cotton short fibers, nylon short fibers having intermediate elasticity between elasticity of main rubber which forms the ribs and elasticity of the cotton short fibers, and zinc powders.
Patent Document 9 discloses a V-ribbed belt in which a compression rubber layer includes para-aramid short fibers; the para-aramid short fibers protrude from side surfaces of ribs; and the protruded para-aramid short fibers are fibrillated.
Patent Document 10 discloses a V-ribbed belt in which a compression rubber layer includes cotton short fibers and para-aramid short fibers which protrude from side surfaces of ribs; the protruded para-aramid short fibers are fibrillated; and the cotton short fibers and the para-aramid short fibers are mixed in a rubber composition of the compression rubber layer in an amount of 10 to 40 parts by weight, and 5 to 10 parts by weight, respectively, relative to 100 parts by weight of the rubber component in the compression rubber layer.
Patent Document 11 discloses a V-ribbed belt in which at least part of short fibers buried in V-shaped ribs which form a compression rubber layer is para-aramid fibers mixed in a rubber component in amount of 5 to 20 parts by weight relative to 100 parts by weight of the rubber component, and the para-aramid short fibers protruding from side surfaces of the V-shaped ribs are fibrillated.
Patent Document 1: Japanese Patent Publication No. 2006-266356
Patent Document 2: Japanese Patent Publication No. 2007-120526
Patent Document 3: Japanese Patent Publication No. 2004-257459
Patent Document 4: Japanese Patent Publication No. 2004-232743
Patent Document 5: Japanese Patent Publication No. 2004-176904
Patent Document 6: Japanese Patent Publication No. 2004-150524
Patent Document 7: Japanese Patent Publication No. 2004-125012
Patent Document 8: Japanese Patent Publication No. 2003-202055
Patent Document 9: Japanese Patent Publication No. 2001-254782
Patent Document 10: Japanese Patent Publication No. 2001-165244
Patent Document 11: Japanese Patent Publication No. H07-151191